Indiana corrections facilities get biomass boilers

Four Indiana prisons will be powered partially by biomass by the end of the year, as part of an Indiana Department of Correction green initiative.

Biomass boilers are being installed at the facilities, constituting four separate projects from contracts with Johnson Controls Inc. Two of the projects involve completely replacing the natural gas boiler tank, replacing the stoker/grate, retrofitting the refractory and adding a new fuel storage and delivery system to handle the biomass. The other two will retrofit existing natural gas boiler systems to burn biomass and take the same remaining steps as the other projects, according to Courtney Figg, IDOC media liaison.

Pendleton Correctional Facility started operating its large biomass boiler Oct. 15; the large boiler at Westville Correctional Facility will be operational by the end of the month; and a large boiler at Indiana State Prison, Michigan City, will be on line in December, Figg said. A small boiler has been in operation at Putnamville Correctional Facility since early 2008. The small boiler burns only wood chips, while the larger ones can handle any type of biomass that can be chipped or turned into pellets, including corn and switchgrass. The large systems will require about 14,000 tons of biomass delivered annually. The IDOC anticipates it will produce part of its fuel needs in the future through farming, pellet mill operations and pallet recycling operations, Figg added.

The biomass boilers use a simple combustion system with a stationary grate. The biomass is pushed slowly across the fixed grate by an auger and heated from the top and bottom, Figg said. "This type of system is proving itself to be both reliable and effective," she said. The biomass systems will run complementary to the natural gas boilers. "Although each of the larger boilers technically has enough output to handle the entire load at its facility, IDOC intends to run each boiler at a base load each year and adjust the load of its companion natural gas boiler accordingly," Figg said.

The conversion to biomass power at the four locations will save the IDOC about $36 million over the next 10 years, plus minor operational savings associated with the boilers, according to the IDOC. The smaller Putnamville boiler cost about $2 million, while the three larger boilers cost about $3.1 million each, according to Figg. The savings, however, on the large boilers is expected to be around $1.5 million per year, she said, and the small boiler will pay for itself within 10 years, while providing additional savings. That savings is based on the cost of replacing natural gas with biomass fuel. The IDOC will obtain biomass at $4.11 per million Btu (MMBtu) from a local supplier, compared with the current cost of natural gas: $8.50 MMBtu.

The projects are funded through an Energy Performance Contract. The contracts allow certain state agencies to borrow capital from a lender who can then issue tax exempt bonds on the loan. They typically allow for repayment over 10 to 20 years out of savings generated from the projects, Figg said.